A hallmark feature of cancerous cells is uncontrolled proliferation. Among the differences that have been discovered between tumor and normal cells is resistance to the process of programmed cell death, also known as apoptosis (Ambrosini et al., Nat. Med., 1997, 3, 917-921). Apoptosis is a process multicellular organisms have evolved to prevent uncontrolled cell proliferation as well as to eliminate cells that have become sick, deleterious, or are no longer necessary. The process of apoptosis involves a multistep cascade in which cells are degraded from within through the concerted action of proteolytic enzymes and DNA endonucleases, resulting in the formation of apoptotic bodies that are then removed by scavenger cells. Research to date has shown that much of the intracellular degradation is carried out through the action of the caspases, a family of proteolytic enzymes that cleave adjacent to aspartate residues (Cohen, Biochemistry Journal, 1997, 326, 1-16).
The finding that most tumor cells display resistance to the apoptotic process has led to the view that therapeutic strategies aimed at attenuating the resistance of tumor cells to apoptosis could represent a novel means to halt the spread of neoplastic cells (Ambrosini et al., Nat. Med., 1997, 3, 917-921). One of the mechanisms through which tumor cells are believed to acquire resistance to apoptosis is by overexpression of Survivin, a recently described member of the IAP (inhibitor of apoptosis) caspase inhibitor family. To date, overexpression of Survivin has been detected in tumors of the lung, colon, pancreas, prostate, breast, stomach, non-Hodgkin's lymphoma, and neuroblastoma (Adida et al., Lancet, 1998, 351, 882-883; Ambrosini et al., Nat. Med., 1997, 3, 917-921; Lu et al., Cancer Res., 1998, 58, 1808-1812). A more detailed analysis has been performed in neuroblastoma where it was found that Survivin overexpression segregated with tumor histologies known to associate with poor prognosis (Adida et al., Lancet, 1998, 351, 882-883). Finally, Ambrosini et al. describe transfection of HeLa cells with an expression vector containing a 708 nt fragment of the human cDNA encoding effector cell protease receptor 1 (EPR-1), the coding sequence of which is extensively complementary to the coding strand of Survivin (Ambrosini et al., J. Bio. Chem., 1998, 273, 11177-11182) and which potentially acts as a Survivin antisense RNA. This construct caused a reduction in cell viability. Methods for modulating apoptosis and for reducing the severity of a pathological state mediated by Survivin using agents that modulate amounts or activity of Survivin are disclosed in WO 98/22589, which also discloses the EPR-1 coding strand/Survivin antisense construct described by Ambrosini et al., supra.
Survivin has recently been found to play a role in cell cycle regulation. It has been found to be expressed in the G2/M phase of the cell cycle in a cycle-regulated manner, and associates with microtubules of the mitotic spindle. Disruption of this interaction results in loss of Survivin's anti-apoptotic function and increased caspase-3 activity during mitosis. Caspase-3 is associated with apoptotic cell death. It is therefore believed that Survivin may counteract a default induction of apoptosis in G2/M phase. It is believed that the overexpression of Survivin in cancer may overcome this apoptotic checkpoint, allowing undesired survival and division of cancerous cells. The Survivin antisense construct described by Ambrosini above was found to downregulate endogenous Survivin in HeLa cells and to increase caspase-3-dependent apoptosis in cells in G2/M phase. Li et al., Nature, 1998, 396, 580-584.
As a result of these advances in the understanding of apoptosis and the role that Survivin expression is believed to play in conferring a growth advantage to a wide variety of tumor cell types, there is a great desire to provide compositions of matter which can modulate the expression of Survivin. It is greatly desired to provide methods of diagnosis and detection of nucleic acids encoding Survivin in animals. It is also desired to provide methods of diagnosis and treatment of conditions arising from Survivin expression. In addition, improved research kits and reagents for detection and study of nucleic acids encoding Survivin are desired.
Currently, there are no known therapeutic agents which effectively inhibit the synthesis of Survivin. Consequently, there is a long-felt need for agents capable of effectively inhibiting Survivin expression in tumor cells. Antisense oligonucleotides against Survivin may therefore prove to be uniquely useful in a number of therapeutic, diagnostic and research applications.